It is safe to say, that Firefox will not be Firefox anymore as far as extensions go, but instead will become yet another Chrome-clone.
A quote from a blog post I read about Firefox as a friend is going to die so I wanted to quickly echo an opinion I have off the top my head without being too technical:
I personally don’t see how implementing a common set of APIs or a spec that the rest of the browser vendors agreed on and implemented is turning Firefox into a chrome-clone.
WebExtensions’ concept is by far implemented everywhere else except in Firefox. So implementing that here is just as beneficial as when W3C publishes a spec about Flexbox or WebRTC or CSS Logical Properties (wink wink) and chrome implements that, and then Firefox implements it too: that. is. not. following. chrome, it’s called making the web and the web’s content more compatible, and if we are to sit in a corner and implement our own exclusive stuff we will only become another Microsoft of year 2000 with its ActiveX technology where the only way to have the luxury of accessing its features is if developers built their websites mainly for IE.
We as Mozilla call for a web that can give the people their choice, so I think our users deserve the choice of running addons that are as good as the ones in Chrome, without switching to Chrome.
Overly attached ads
I’m a recent graduate, and while I was studying (and working on my graduation project) I’ve seen my friends using Firefox but the truly sad thing is that their Firefox is bloated with ads on literally every inch of the screen, ads that won’t even come to you in your worst nightmares, some of them are being positioned as absolute and they just never go away no matter what page you visit (oh mercy).
And I’m just tired of cleaning out relatives’ browsers from malware and malicious addons just because they installed this or that software on their computers!
The new addons approach aims to make that part of the never-coming-back past, which is another principle we as Mozilla work toward: privacy and personal safety of the web’s users.